Sang-i Chakmak (Tappeh Sang-e Chakhmaq, Sange Chaxmaq, Chakhmagh) is a Neolithic archaeological site located about 1 km (0.62 mi) north of the village of Bastam in the northern Semnan Province of Iran, on the southeastern flank of the Elburs Mountains.

The site represents quite well the transition from the aceramic Neolithic phase in the general area; this was taking place during the 7th millennium BC.

It includes several settlement mounds, of which two were excavated in 1971-1977 by a team from the Tokyo University of Education (now Tsukuba University)[1] Another related site is Deh Kheyr, Semnan, located only 4 km (2.5 mi) from Sang-i Chakmak.

The western settlement is an approximately 3 m high mound with a diameter of about 80 m, and contains five cultural layers.

In one of these small rooms without hearth in layer II some highly stylized clay figurines were found.

Layers VI-III contained multi-dimensional rectangular dwellings with outbuildings, often with a small work area and an oven.

A skull of a young woman was also found; it was covered with a decorated pot of a type known from the site of Tepe Sialk.

Also, around 4500, Anau IA ware appears at the site, with simpler geometric and linear designs, and less finely made ceramics.

These indications have been confirmed by the studies of Toshio Nakamura from the Center for Chronological Research of Nagoya University in 2014.